For months, athletics became synonymous with a drug few had ever heard of and the problem for the authorities increased considerably when it was revealed that nandrolone occurs naturally in the body as well as a variety of foodstuffs.

When athletes are tested for the steroid, scientists actually search for nandrolone's waste product, 19-norandrosterone.

If this is detected in urine it is regarded as proof that nandrolone has been present in the athlete's body.

For men, the limit is two nanograms of the waste-product per millimetre of urine. For women the limit rises to 5ng/ml.

How it got there

The testing procedure, as a result, holds no particular mystery. The problem, however, is that once detected, no-one can be sure how the substance arrived in the body.

A comprehensive, independent survey recently carried out by a team of British scientists identified four possible sources of nandrolone:

That it could have been injected, though this is unlikely as all top athletes know it is easily detectable.

That it could have occurred from eating a large quantity of wild boar offal - again extremely unlikely.

That it may have occurred after pills or food containing either of the above, were digested knowingly or otherwise.

That minute amounts of nandrolone occur naturally in the body - though testing has discovered this rarely exceeds 0.6ng/1000ml.

Clearly, the problem for the authorities comes in the third explanation - whether athletes knowingly took pills or other products containing the steroid.

The chief executive of UK Athletics, David Moorcroft summed up the problem when he conceded: "It's possible tests do indicate guilt.

"It is conceivable some of them are guilty, that all of them are guilty or that - possibly - none of them are."

Linford Christie is awaiting an IAAF arbitration hearing

It is certainly a delicate matter and, while research continues, the authorities can do little except ask the athletes concerned for an explanation.

British bobsleigher Lenny Paul, claimed his positive test was the result of eating too much spaghetti bolognese, while Baumann, who has since had his suspension lifted, maintained the substance was injected into his toothpaste by an unknown foe.

Christie, who was said to have more than 100 times the acceptable level of nandrolone in his system, said his samples had been repeatedly taken in and out of the fridge and even left in a car overnight.

He was cleared by UK Athletics of any wrongdoing, but must now wait for an IAAF arbitration panel to decide his future.

Cadogan and Walker were similarly referred, despite being cleared by UK Athletics, though the Scot is hoping to overrule that decision at a high court meeting in London next month.